The present invention relates similarly to the field of lighting systems, such as fluorescent light systems. More particularly, the invention relates to a lighting system employing pulsed mode driving techniques to utilize emissions in an afterglow regime.
A wide variety of lighting systems are known and are currently in use. The systems include a variety of incandescent and gaseous emissive systems which produce visible light when a drive signal is applied to input terminals. In systems employing gaseous media, a gas or gas mixture is typically provided in a tube, or translucent or transparent shell. A discharge is produce through the gas as signals are applied to anode and cathode structures. The discharge produces emissions from the gas which may be transmitted directly through the shell or which may be transformed to other wavelengths by various materials disposed on or about the shell. Typical materials on fluorescent lamps include various phosphor mixtures which convert wavelengths of emissions from the gas to desired spectra.
The overall efficiency of a lighting system employing a gaseous medium for emissions may be considered a ratio of input power to output light emission. In general, however, specific gases and gas mixtures will emit light in specific bands or spectral ranges when excited by the input signals and the resulting discharge. Depending upon the energy levels and bands emitted by the gaseous medium, the phosphors convert the energy to other wavelengths, typically within a visible light spectrum comprising wavelengths of from approximately 420 nm to approximately 760 nm.
For example, mercury gas lamps typically produce emissions within specific bands of the spectrum, including a band of approximately 254 nm wavelength, and another at approximately 365 nm. Phosphors used to convert these emissions to a visible spectrum, however, do not typically have the same conversion efficiencies at the different wavelength bands. Specifically, currently used phosphors on certain low pressure discharge lamps do not as efficiently convert more intense 254 nm emissions from mercury as they do 365 nm emissions. While adjustments can be made to the phosphors, and to the gas, there is a need in the art for improved techniques for controlling the emissions such that greater efficiencies can be maintained by relying upon the longer 350 nm wavelengths for higher ratios of the overall energy output.